Human vibration comfort has attracted more attention in recent development effort by OEM's and suppliers. This is due to the new phase of NVH improvement and competition in vehicle design. Improving human ride comfort has always been an issue for vehicle component designers and manufacturers. For seating and interior integrators, a great deal of effort has been focused on improving the ride comfort.
Vibration transmissibility has been used as an indicator to measure the comfort of ride by researchers for many years. The ratio of acceleration of the seat cushion or seat back to that of the floorpan is used to measure the transmission of vibration from vehicle to the human occupant. A difficulty arises when a large number of human occupants are needed for a valid test or a component quality evaluation. Component suppliers usually cannot afford such expensive tests during prototype development stage. The number of tests involved to improve the quality of seating systems requires a quicker and more repeatable way to measure the seat vibration performance.
A rigid mass dummy has been used to set a "benchmark" for the seat vibration performance measurement. The rigid mass dummy, however, cannot provide a similar transmissibility measurement to that of a human so its application is largely limited.
In Gu, Y., "A Comparison Test Of Transmissibility Response From Human Occupant And Anthropodynamic Dummy", SAE paper 980655 dated Feb. 23-26, 1998, a spring-mass dummy is described which was designed to match the human response in low frequency in a vertical direction. A six-axis hydraulic shaker table was employed as the excitation source to the occupied seat. Two seat samples, both measured with human occupants before, were used. For simplicity and comparison, a sweep sine signal in the vertical direction was used as the excitation signal. The transmissibility results measured for the dummy-loaded seat were compared to those of human occupants. The vibration response from a dummy-occupied seat was correlated to that from a human-occupied seat. A consistent relation was shown between the two measurements. However, there are problems of accuracy and stability of transmissibility measurement when utilizing such a spring-mass dummy.
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